Device for measuring the impedance to flow of a natural or prosthetic vessel in a living body

Abstract

A highly automated device to measure the impedance to fluid flow of a vessel by means of direct injection at normal physiologic pressures. The device produces objective impedance data including dynamic impedance, capacitance, and Direct Current resistance, without operator induced error. The device can be used for intraoperative impedance measurements by directly cannulating the vessel under study. Non-operative impedance measurement is performed by means of percutaneous catheters. The device can also inject imaging materials or a lytic solution into the vessel while also measuring vessel impedance.

I claim: 
     
       1. A device for measuring the impedance characteristics of a vessel in a living body, said device comprising: an automatic injection means for injecting fluid into a vessel, flow of said fluid directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of said vessel;   a feedback control means, operably coupled to said automatic injection means and said pressure sensor means, for controlling fluid injection by said automatic injection means so as to maintain luminal pressure of said vessel at a selected value; and,   a means for determining the flow per unit time injected by said automatic injection means, whereby the flow rate necessary to maintain luminal pressure at the selected value can be determined.   
     
     
       2. The device of claim 1, further comprising a means for isolating said vessel from naturally occurring physiological flow, so that luminal pressure in said vessel is generated exclusively by the injection of fluid by said automatic injection means. 
     
     
       3. The device of claim 2, further comprising: a means for automatically sequencing the feedback control means to generate at least two selected values of luminal pressure in said vessel, thereby automatically determining the flow rate necessary to maintain each of said selected values of luminal pressure.   
     
     
       4. The device of claim 3, further comprising: a second pressure sensor means for measuring pressure in the vessel upstream from the point fluid is injected into the vessel by the automatic injection means, so that luminal pressure naturally occurring in the vessel can be determined.   
     
     
       5. The device of claim 4, further comprising: a means, operably coupled to such second pressure sensor means and said automatic sequencing means, for automatically selecting the at least two values of luminal pressure within the range of naturally occurring luminal pressures detected by said second pressure sensor means.   
     
     
       6. The device of claim 4, wherein an operator can select the at least two luminal pressure value. 
     
     
       7. The device of claim 1, wherein said feedback control means causes said automatic injection means to cease injection after a preselected luminal pressure has been maintained in the vessel for a set period; and, wherein said device further comprises a means associated with said pressure sensor for monitoring luminal pressure decay occurring immediately after cessation of injection, thereby producing pressure-time decay data which can be used to calculate capacitance of the vessel. 
     
     
       8. A device for measuring the capacitive characteristics of a vessel in a living body, said device comprising: an automatic injection means for injecting fluid into a vessel, flow of said fluid directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of said vessel;   a control means, operably coupled to said automatic injection means and said pressure sensor means, for controlling the rate of fluid injected by said automatic injection means so as to charge the vessel with a selected lumen pressure, followed by a cessation of injection flow, and   a means associated with said pressure sensor means for monitoring luminal pressure decay occurring immediately after cessation of injection flow, thereby producing pressure-time decay data which can be used to calculate capacitance of the vessel.   
     
     
       9. The device of claim 8, further comprising a means for isolating said vessel from naturally occurring physiological flow, so that luminal pressure in said vessel is generated exclusively by the injection of fluid by said automatic injection means. 
     
     
       10. The device of claim 9, further comprising: a means for automatically sequencing the control means to at least two selected values of charging luminal pressure, with pressure decay measurements taken for each selected value, so that vessel capacitance can be measured over a range of luminal pressures.   
     
     
       11. The claim of claim 10, further comprising a second pressure sensor means for measuring pressure in the vessel upstream from the point fluid is injected into the vessel by the automatic injection means, so that luminal pressure naturally occurring in the vessel can be measured; and a means operably coupled to said second pressure sensor means and said automatic sequencing means, for automatically selecting the at least two values of luminal pressure within the range of naturally occurring luminal pressures detected by said second pressure sensor means. 
     
     
       12. The device of claim 10, wherein an operator can select the at least two luminal pressure values. 
     
     
       13. The device of claim 9, wherein said control means maintains luminal pressure at a selected value for a set time period, prior to the cessation of fluid injection, and, wherein said device further includes a means for monitoring the flow per unit time injected by said automatic injection means that is necessary to maintain said selected luminal pressure. 
     
     
       14. A device for measuring the dynamic impedance characteristics of a vessel in a living body, said device comprising: an automatic injection means for injecting fluid into said vessel in a pulsatile manner, flow of said fluid directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of the vessel during and between each pulsatile injection;   a control means for causing said automatic injection means to inject a pulsatile fluid flow to generate a luminal pressure-time profile generally matching a target fluid pressure-time profile; and,   a means for determining the instantaneous injected flow rate occurring during each pulsatile injection.   
     
     
       15. The device of claim 14, further comprising a means for isolating said vessel from naturally occurring physiological flow, so that luminal pressure in said vessel is generated exclusively by the injection of fluid by said automatic injection means. 
     
     
       16. The device of claim 15, where in said control means uses luminal pressure detected by said pressure sensor means as feedback control and includes a means for successively altering the injected pulsatile flow profile until the resulting pressure-time profile in the vessel lumen matches the target pressure-time profile. 
     
     
       17. The device of claim 15, wherein said control means further includes a means for measuring the pressure-time profile in the vessel at a point removed from the point fluid is injected by said automatic injection means, and wherein said target pressure-time profile is said measured pressure-time profile. 
     
     
       18. The device of claim 15, wherein said control means further includes a means for measuring the pressure-time profile in a second vessel, and wherein the target pressure-time profile is the said measured pressure-time profile. 
     
     
       19. A device for controlling the injection of an imaging fluid into a vessel, said device comprising: an automatic injection means for injecting an imaging fluid into the vessel for imaging the vessel, flow of said imaging fluid directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of said vessel; and   a feedback control means, operably coupled to said automatic injection means and said pressure sensor means, for controlling the rate of fluid injected into the vessel so as to achieve, but not exceed a preselected luminal pressure.   
     
     
       20. The device of claim 19, wherein said automatic injection means generates a pulsatile flow pattern generally matching a target pressure time profile, so as to allow for injection of the contrast material at the vessels naturally occurring flow velocities. 
     
     
       21. A device for controlling the injection of an imaging fluid into a vessel, said device comprising: an automatic injection means for injecting an imaging fluid into the vessel for imaging the vessel, flow of said imaging fluid directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of said vessel;   a feedback control means, operably coupled to said automatic injection means and said pressure sensor means, for controlling the rate of fluid injected into said vessel so as to achieve a preselected luminal pressure so that imaging fluid can be injected at a safe pressure; and,   a means for determining the flow per unit time injected by said automatic injection means, whereby the flow rate necessary to maintain luminal pressure at the selected value can be determined and flow impedance can be calculated.   
     
     
       22. A device for controlling the injection of a lytic solution into a vessel, said solution intended for the purpose of dissolving an obstruction of said vessel, said device comprising: an automatic injection means for injecting the lytic solution into the vessel, flow of said lytic solution directly generating a change in luminal pressure in said vessel;   a pressure sensor means for measuring luminal pressure of said vessel; and,   a feedback control means, operably coupled to said automatic injection means and said pressure sensor means, for controlling the rate of fluid injected into the vessel so that luminal pressure can be maintained at a preset level, generally not to exceed the normal physiologic pressure experienced by said vessel.   
     
     
       23. The device of claim 22, further including a means for determining the flow per unit time injected by said automatic injection means, whereby the flow rate necessary to maintain luminal pressure at the preset level can be determined and flow impedance can be calculated.